cowbird vs New World blackbird

cowbird and New World blackbird both are nouns.

Word	Noun	Adjective	Verb	Adverb
cowbird	Yes	No	No	No
New World blackbird	Yes	No	No	No

As nouns, New World blackbird is a hypernym of cowbird; that is, New World blackbird is a word with a broader meaning than cowbird:

cowbird: North American blackbird that follows cattle and lays eggs in other birds' nests
New World blackbird: any bird of the family Icteridae whose male is black or predominantly black

Other hypernyms of cowbird include blackbird.

cowbird (noun)	New World blackbird (noun)
North American blackbird that follows cattle and lays eggs in other birds' nests	any bird of the family Icteridae whose male is black or predominantly black